Machine-switching telephone-exchange system.



` C.AL. GOODRUM. MACHINE SWITCHINGTELEPHONE EXCHANGE SYSTEM.

APPLICATION FIEED JUNE 22H19? r UNITED sTATEs PATENT OFFICE. A'

CHARLES L. GOODRUM, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS,TO

`WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

MACHINE-SWITCHING TELEPHONE-EXCHANGE SYSTM.

` Toell ywhom t maywncern: i Be it known that I, CHARLES L. GooDRUM,

a citizen of the United States, residing at and exact description.

This invention relates to lmachine switching telephone exchange systemsof the stepby-step type, and"particularly to a system of this typewherein trunks lead from the connectors to private branch exchange l5switchboards.

It is customary to assign to a private branchvexchange 'a single numberjust as if it were an ordinary substation, and to set the connectorswitch in the usual way under control oi' a suitable sender upon thefirst of vsuch trunk lines. The connector then tests such lineautomatically. It' the same is busy, it passes onand tests the remainingtrunk lines in succession until an idle one is found,

whereupon it extends the call in the wellknown manner. In case all thetrunks are busy, a busy signal is transmitted to the calling party. A,

It is the object of this invention to provide a new and improvedconnector circuit arrangement for effectively performingthese functionsin a two-wire system, wherein the private branch exchange trunks aregrouped upon special connectors, and wherein the connectors arecontrolled by steering or side switches.

In the circuit arrangement of this invention, 'the operation of theconnector' is the same as those well known in the art/up to the y 40point of testing the first of the private branch exchange trunksassigned to the particularfnumber involved, .that is to say, the side orsteering switch in position l places .the primary stepping magnet of theconnector undercontrol of the stepping `rlay lin order .to set theyconnector brushes in accordance with the tens digit of the wantedsubscriberrs number. Upon the termination fof this' operation, the side'switch places the 'secondary stepping magnet under control of thestepping relay to .set the connector onto the first of the equivalentlines leading to the Specication of Letters Patent.

Patented oct. 24, 191e.

Application led I une 28, 1915. SerialNo. 36,719.

private branch exchange corresponding to the number in question. If theline is idle the side switch control magnet releases the side switchinto the ringing position.' It is from this point on that the presentcircuit arrangement differs from the prior art.

In accordance with the invention, 'the side switch escapement magnet ismade slow-acting, and during the transmission of the units digit ismaintained energized by impulses from the armature and backcontact ofthe stepping relay. Thus, when the sender restores and maintains theline circuit closed, its armature begins to drop away. The relationbetween the side switch A'escapement mechanism and the escapementmagnet-armature is such,'however, that it does not release the sideswitch until it reaches the yend of its stroke. Before itreaches the endof its stroke, it closes a circuit including its own winding, thesecondary stepping magnet winding and the connector test brush. Nowunder the assumed condition that the first line is busy and hasgroundupon its test terminal, the side switch escape-ment magnet closes acircuit for the said stepping magnet, which steps the brushes onto thenext set of terminals which represents an equivalent line to that justtested. In case this line is idle, its test terminal is ungrounded andthe escapement magnet deenergizes and releasesthe side switchinto theringing position. It, on the contrary, this line is also busy, theescapement magnet again attracts its armature before it has fallen backfar enough to release the side switch, and near the end of its forwardstroke again breaks its own circuit and that of the secondary steppingmagnet and again ,denergizes, its armature, upon closing its backcontact, giving another impulse to the secondary stepping magnet. Inthis manner the connector is stepped ahead until rin ungrounded testterminal is reached, when connection ismade to such line. Each group oflines leading to the same private ranch exchange or to the same station,2is to owed by a set of contacts upon whichv thm-connector brushes cometo rest, if all the Atrinke are busy, and transmits a busy signal toth.r calling party in the well-known manner.

Referring. to the drawings,- the 'connectorl circuit only is shown, 1tbeing understood that a connection would ordinarily lead from thecalling substation A through one or more finders or equivalent switchesand group selectors, and finally through the connector shown, to theprivate branch exchange.

Figure 1, therefore, shows only the connector circuit of this invention,and Fig. 2 is a detail view of the 'side switch escapement mechanism andthe control magnet therefor.

The invention will be readily understood from a description of theoperations involved in setting up a connection.A The removal-of thereceiver by the callingv party at substation A initiates-the movement ofthe line finder. lVhen such finder has connected with the calling line,the stepping relay 10 at the first selector is energized over thefollowing circuit: free' pole of battery, left winding of said relay,conductors 11, 12, brush 13, terminal 14, line conductor 15 through thetelephonie apparatus at substation A, line conductor 1G, terminal 17,brush 18, conductors 19 and 20, right winding of relay 10 to ground.Relay 10 thereupon closes the following circuit for slowacting relay 21as follows: free pole of the battery, relay 21. conductors 22 and 23,armature and back contact of relayv 2l, conductors 25 and 26, armatureand front con.

tact of relay 10 to ground. The slow-acting relay 2l thereupon, at itsleft armature and back contact, opens the circuit of release conductor30 leading back to the line finder or line' finders and prepares acircuit for slow-acting magnet 27. which is' the escapement magnet ofthe side switch. lhe calling party now operates his senderl andinterrupts the line circuit a number of times. corresponding to the tensdigit of the wanted line.

Each time the. armature of relay 10 closes its back contact, an impulseis sent tothe primary stepping magnet 32 of the, connector over thefollowing circuit: 't'reo pole ot the battery, magnet 32. side switcharm 3?) and -its first contact. conductor 2H. 35. right armature andtrout contact of relay 2l, conductor 29. armature and backcontzurt otrelay l() to lground. 'l`he magnet 32 thus steps the hruslua.l Ilo, 3Tand 33 into operative relation to the group et' terminals containing thegroup ot' trunks leading to the desired private hranch exchange. Uponthe irst closure ot' the bach' Contact of relay l0,

the slow escaluincnt magnet was yenergized over the following path:i'ree pole. of battery` lett winding ot' magnet 27, conductors 2S. 35.right armatury and t'ront contact ot relay 2l. conductor 2.) to ground.lVhen the sender 3l completelyrestores and maintains the line circuitclosed. the circuit traced for the 4escapement magnet 27 is opened atthe armature and back contact ot' stepping relay 10, and after aninterval the magnet 27' allows its armatures to re-y magnet 39, sideswitch arm 33 and its second contact, conductors 34 and 35, rightarmature and front contact of relay 21, conductor 29, armature and backcontact of relay 10, to ground. The magnet 39 therelupon steps thebrushes in a secondary direction over the terminals of the selectedgroup. The first retraction of the armature of relay 10 again closed acircuit for the side switch cscapement magnet 2l over the circuitpreviously traced. When the sender completely restores and maintains theline circuit closed, the maintained attraction of the armature ot' relay10 opens the circuit ot' slow-acting escapement ma net 27. Assuming nowthat the first o? the private lnanclr exchange trunks, whose terminalsare indicated by the numbers 40, 41,' 42 is busy. the multiple testterminals l2 thereof will be. grounded. Thus, remembering that the sideswitch iS now in the second position. the armature of the slow-actingescapement magnet 2T, at the beginning of its reti-active movement,closes the following circuit t'or the secondary stepping magnet 39 tostep the brushes 3G, 37, 3S on to the next trunk, which is an equivalentline leading to the same private h'aneh exchange: tree pole of thebattery, magnet 3l), side switclt arm 33 and its second contact,conductors 34, 2S, armature and back contact ot' cscapement magnet 2T,conductor 13, side switch arm -H and its second Contact, conductor 45,test brush 3S to grounded test terminal 42. Simultaneously with theclosureI of this circuit through the secondary stepping magnet 39, a`circuit is closed in pa rallcl therewith for the side switch escapementmagnet 2T. This circuit is as follows: jree pole of battery. leftwinding of magnet 2T, armature and back contact of magnet 2T. conductor43, sido switch arm -l-i and its second contact. conductor 45tcSt brush38 to said grounded test terminal. Thus, the magnet 2T again attractsits armature bet'orc. it has lnovcd a suliicient distance to releaselthe side switch into the ringing position. This will he clear fromaconsideration ot' Fig. 'lhis ignre shows the side switch magnet 2i'energized and the side switch iu its second position. This is thecondition that, prevails just as the sender 221 restores and maintainsthe circuit of lstepping' relay 10 closed@r It will be noted that thepin 5 6 on the armature 52 of the escapement magnet 27, maintains openthe conrmiection between springs 50 and 51', which correspond to thearmature 57 and back "contact 58 of the magnet 27 in Fig. 1. Thisarmature 52 is pivoted at 59 upon the same axis as that of the arni 60to which the toothed' U-shaped spring 70 of the escapein engagement withthe third tooth G3 ofv the lower member 64.

Referring back to Fig. 1, it will be ap\l parent therefore that as longas the test brush 38 encounters grounded test contacts 42, whichrepresent blsy lines, impulses will be sent to the secondary steppingmagnet 39. `When, however, the test brush encounters a test contact 42from which ground is removed, which indicates that the line representedthereby is idle, there is no circuit for the side switch magnet 27, andit allows its armature to retract to its extreme position, thusreleasing the side switch into the third position. Side switch arm 44 inthis position grounds the multiples 42 of the seized trunk to cause thisline to test busy to other connectors. In position 3, the genera-- toris connected in circuit with the seized trunk in the well-known manner.Since this forms no part of the present invention, the bell at theprivate branch exchange is not shown. -It will be understood that theoperator will respond to the ringing of the bell 0r the lighting of alamp, as the case may be, and by depressing a key or inserting a plug ina jack, bring her head set in circuit to respond to the calling partyand determine his wants. Upon the insertion of such head set into thecircuit, the relay 24 which is marginal, at its armature 'and backcontact opensthe short-circuit about the -rightihand winding of the sideswitch escapement magnet 27, whereupon the side switch becomesenergized. This circuit is as follows: free pole of battery, relay 21,conductors 22, 74, 75, 2G, armature and front contact of stepping relay10-to ground. The side switch is released into the fourth position bythe energization of the magnet 27 at this time, since the tooth whichordinarily stops the arm 83 is removed from the upper member 55, and thearm 83 therefore is not stopped until it reaches the tooth '76, at whichtime the side switch arms 71 are in contact with the fourth set ofterminals. Current is fed to the called party over the windings of thecalled supervisory relay 65 in the wellknown manner.

When the calling and called partles hang up their receivers the releasemagnet 49-is energized over the following circuit: free pole of thebattery, release magnet 49, conductor 66, primary off-normal spring PON(now closed), right armature and back contact of relay 65, conductor 82,left armature and back contact of relay 2l, conductor 30,

conductor 67, left armature'and back con- Y tact of relay 65, conductor6'8, right armai ture and back contact of relay 21, conductor- 29, leftarmature and back contact of relay 10 to ground. The release magnet 49there-k upon restores the connector and side switch. When the connectoris completel restored it opens ott-normal contact PO thus deenergizingmagnet 49. The closure of the armature of relay 10 to its back contactgrounds conductor 78, leading back to the group selectors and finders or-`e uivalent switches, to release the same in t e well-V known manner.

Each group of terminals, representing a group of trunks leading to thesame substation or to the same private branch exchange operators.switchboard, as the case may be, is followed by a set of contacts 79,80, 81. Contact 81 has a busytone thereon. The connector brushes willalways come to rest upon this 'set of terminalsif all the trunks arebusy, and give a busy signal to the calling party. I

What is claimed is:

1. In a telephone system, the combination with a plurality of' lines, anautomatic switch wherein said lines terminate in groups and having atest terminal for each line and a test wiper, means for grounding testcontacts of-busy lines, a side switch, a

spring adapted to advance thesame, of a slow-acting control magnet forsaid side switch constructed and arranged to allow said spring toladvance said side switch only after its armature has retracted apredetermined distance, a stepping magnet, -a sender for' operating thesame to set said test wiper on the first one of a group of said testterminals, and circuits including grounded test terminals of busy lines,said test wiper, and said control and stepping magnets, and leadingthrough an armature and back contact of said control magnet andelosedafter said armature has retracted a predetermined distance less thanthat necessary to release the side switch.

2. In a telephonesystem, the combination with a plurality of groups oflines, each group running` tol the same substation, an automatic switchwherein said groups terminate and having a test terminal for each lineand a test wiper, means for grounding test contacts of busy lines, asidegwitch, a spring adapted to advance the same, of a slow-actingcontrol magnet for said side switch constructed and arranged to allowsaid spring to advance said side switch only after its armature hasretracted a predetermined distance,y a stepping magnet, a sender foroperating the same to set said test wiper on the Afirst one of a groupof said test terminals, and circuits including grounded test terminalsof busy lines, said test wiper, and said control and stepping magnets,and leading through an armature and back contact of said control magnetand closed after said armature has retracted a predetermined distanceless than that necessary to release the steering switch.

3. In a telephone exchange system, the combination with a plurality ofgroups of lines, each group running to the same substation, an automaticswitch wherein said roups terminate and having a test terminal oreachline and a test Wiper, means for giving said wiper a movement in aprimary direction vunder control of said sender,

'a stepping magnet for moving said wiper 1n a secondary direction undercontrol of said sender and into engagement with the first line of thedesired group, means for grounding test contacts of busy lines, a sideswitch, a snring adapted to advance the same of a slow-acting controlmagnet for said side switch constructed andarranged to allow said springto advance said slde switch only after its armature has retracted apredetermined distance, and circuits including' grounded test terminals'of busy lines, said test wiper,'and said control and stepping magnets,and leading through an armature and back contact of said control lmagnet and closed after saidv armature has retracted a predeter1uineddistance less than that necessary to rel-case the sideswitch.

4. In a telephone system, the combination with an automatic selectorhaving fixed and movable terminals including test terminals and a motormagnet, of a side Aswitch for controlling the selector and beingprovided with a magnet and a contact closed as said magnet isdenergized, and a circuit for the selector motor magnet including testterminals of said selector and said contact of the side switch magnet.

5. In a telephone exchange system, the combination with a plurality oflines, an automatic switch wherein said lines terminate in groups andhaving a test terminal for each line, and a test wiper, means forchanging the electrical condition of the test termmals of busy lines, asteering switch, means tending to advance the same, acontrol magnet. forsaid steerin switch adapted to allow said means to a vance the same onlyafter its armature has retracted a predetermined distance, a steppingmagnet for said automatic switch, means for settin said test wiper onthe first of a group o test terminals, and circuitsy including testterminals of busy lines, said wiper and said control and steppingmagnets, and including an armature and back contact of said controlmagnetand closed when said armature has retracted a predetermineddistance less than that necessary to release the steering' switch.

In witness whereof, I hereunto subscribe my name this 25th day of June,A. D. 1915.

CHARLES L. GOODRUM.

